The present invention relates to a method and apparatus for controlling an airplane engine and, more particularly, to a method which enables easier control of a reciprocating engine of an airplane and which sets the engine in such an operating condition in a partial power mode as to maximize the efficiency of the airframe and the engine as a whole, and to an apparatus for controlling an airplane engine according to the method.
Conventionally, to control drive of a reciprocating engine of a small plane having a variable-pitch propeller, a drive control system is used in which the engine torque is controlled by means of a throttle and a fuel regulator, and in which the number of revolutions of the propeller is controlled by means of a governor.
That is, the throttle sets the amount of air drawn into the engine, the fuel regulator sets the air-fuel ratio, and the governor controls the load on the engine by changing the propeller pitch, thus controlling the engine so that the engine has a set number of revolutions.
This engine drive control is performed by operating the throttle with a throttle lever, operating the fuel regulator with a mixture lever, and operating the governor with a governor lever. A pilot of the airplane sets the number of revolutions of the propeller governor to a desired number by operating the governor lever, adjusts the throttle opening by operating the throttle lever, and controlling the air-fuel ratio setting in the engine by. operating the mixture lever, thereby obtaining the desired engine output.
In the above-described conventional engine drive operating system for a small plane having a variable-pitch propeller, it is necessary for a pilot to perform troublesome steps of operating the three operating levers in order to obtain the desired engine output.
The publication of U.S. Pat. No. 4,626,170 discloses a normal aspiration engine for an airplane with a variable-pitch propeller, which is designed so that the throttle opening and the set number of governor revolutions can be simultaneously controlled with one lever.
In the engine disclosed in this patent publication, a fuel injection controller is provided to control the amount of fuel injected into the engine according to the amount of air drawn into the engine, and the governor and the throttle valve are connected to one power control lever by a link mechanism. In this engine, the set number of revolutions of the propeller governor and the throttle opening are simultaneously changed according to the amount of operation of the power control lever. When the set number of revolutions of the propeller governor is small, the throttle opening is set to a small value. When the set number of revolutions of the propeller governor is large, the throttle opening is set to a large value.
In general, when an airplane makes a short-distance flight, it flies with full engine power. In contrast, in the course of a long-distance flight, the airplane starts cruising when it reaches a predetermined altitude. During cruising, the airplane flies at 70 to 80% of the maximum engine power. Such power smaller than the maximum power is called partial power. Basically, the fuel efficiency of the engine is improved when such partial power is set.
To consider fuel economy of an airplane, the operating work efficiency of the airframe and the engine of the airplane as a whole, i.e., the flight distance traveled by the airplane consuming a predetermined amount of fuel, including the efficiency of the propeller connected to the engine, i.e., the efficiency at which the engine output is converted into a thrust by the propeller, must be taken into consideration as well as the fuel efficiency of the mounted engine itself.
In the case of the invention described in the specification of U.S. Pat. No. 4,626,170, full opening of the throttle is presupposed with respect to the range of 2000 or more engine revolutions per minute, as shown in FIG. 25. When the throttle is fully open, there is no suction loss in the engine, so that the fuel efficiency of the engine is high.
However, from representation of the relationship between the throttle and the number of engine revolutions and the relationship between the torque and the number of engine revolutions reflecting the former relationship as shown in FIG. 26, it can be understood that a large discrepancy can be seen between an arbitrary point F designating a number of revolutions of 2000 or more and a point G designating the same number of revolutions as the point F on a maximum propeller efficiency line L (on which a relationship expressed by Te xe2x88x9d xcfx81N2 is established between the torque Te and the number of engine revolutions Ne) supposed from the relationship between the torque and the number of engine revolutions.
Therefore, it is possible to say that the invention of the above-mentioned U.S. patent is incomplete in terms of fuel economy conditioned by the efficiency of the airframe and the engine of an airplane as a whole including the propeller efficiency.
In view of the above-described circumstances, an object of the present invention is to provide an airplane engine control method and apparatus which can realize an optimal propeller efficiency when partial power is set in an engine of an airplane, and which can set a good operating condition by improving fuel efficiency of the airframe and the engine of the airplane as a whole.
Another object of the present invention is to provide an airplane engine control method and apparatus which can maintain a propeller-efficiency-maximized condition when partial power is set in a normal aspiration engine of an airplane and thereby realize a good operating condition of the airframe and the engine of the airplane as a whole including fuel efficiency of the engine.
Still another object of the present invention is to provide an airplane engine control method and apparatus which can maintain a propeller-efficiency-maximized condition when partial power is set in an engine with a turbocharger of an airplane and thereby realize a good operating condition of the airframe and the engine of the airplane as a whole including fuel efficiency of the engine.
Yet still another object of the present invention is to provide an airplane engine control method and apparatus which can maintain a propeller-efficiency-maximized condition in accordance with a change in the drag of airplane even when the drag of airplane is changed by, for example, a change in weight during a flight and thereby realize a good operating condition of the airframe and the engine of the airplane as a whole including fuel efficiency of the engine.
Yet still another object of the present invention is to provide an airplane engine control method and apparatus which can improve the controllability of an engine of an airplane to be controlled by a pilot while a propeller-efficiency-maximized condition is maintained to realize a good operating condition of the airframe and the engine of the airplane as a whole including fuel efficiency of the engine.
According to the present invention, there is provided a method of controlling a reciprocating engine with a variable-pitch propeller provided on an airplane, in which suitable partial power is set in the engine, the method comprising setting an engine condition such that a relationship represented by Te xe2x88x9d xcfx81N2 is established with respect to the engine torque (Te), the number of engine revolutions (N) and the atmospheric density (xcfx81) when predetermined partial power is set in the engine.
The inventors of the present invention have achieved the present invention with the aim of improving, as well as the engine fuel efficiency, the fuel efficiency of an airplane conditioned by the efficiency of the airframe and the engine of the airplane as a whole including the propeller efficiency when partial power is set in the engine, and also improving the controllability of the engine to be controlled by a pilot when the partial power is set.
While independent operating systems of a throttle, a fuel regulator, and a governor respectively operated with separate operating levers are conventionally used, one operating lever capable of integrally controlling such three operating systems is provided according to the present invention. To improve the engine controllability, this operating lever is used and operation control is performed by using control means for setting control values for a throttle, a fuel regulator and a governor by comparing the opening angle of the operating lever with prepared maps of the air-fuel ratio, the throttle opening and the number of engine revolutions.
The other object of improving the total fuel efficiency of an airplane according to the present invention corresponds to improving the operating efficiency of the airframe and the engine of the airplane as a whole including the efficiency of the propeller connected to the engine, i.e., the flight distance traveled by the airplane consuming a predetermined amount of fuel, as well as the efficiency of the mounted engine itself, as mentioned above.
To improve the total operating efficiency of an airplane described above, it is necessary to make a study of means for improving the operating efficiency by considering the number of revolutions and the torque of the engine, the propeller efficiency, and the drag of airplane.
A variable-pitch propeller of an airplane according to the present invention is designed so as to obtain a suitable thrust by suitably controlling the pitch angle of propeller blades. Individual propellers connected to different engines vary in propeller characteristics. To study the propeller characteristics of such propellers, it is necessary to consider xe2x80x9cadvance ratioxe2x80x9d and xe2x80x9cpower coefficientxe2x80x9d.
The xe2x80x9cadvance ratioxe2x80x9d is a value obtained by dividing the actual speed of an airplane by the geometrical advancement rate, as expressed by the following equation:       Advance    ⁢          xe2x80x83        ⁢    Ratio    ⁢          xe2x80x83        ⁢    J    =      V    ND  
where V is the actual speed of the airplane, N is the number of revolutions of a propeller, and D is the diameter of the propeller.
The power coefficient is a value obtained by dividing the work input to the propeller by the work of air discharged by the propeller, as expressed by the following equation:       Power    ⁢          xe2x80x83        ⁢    Coefficient    ⁢          xe2x80x83        ⁢    Cp    =            2      ⁢      πTe              ρ      ⁢              xe2x80x83            ⁢              N        2            ⁢              D        5            
where Te is the engine torque, xcfx81 is the atmospheric density, N is the number of engine revolutions, and D is the diameter of the propeller.
In general, the power of an engine is the product of the torque and the number of revolutions of the engine. Essentially, airplanes are designed so that the propeller efficiency is maximum during operation in a full-power mode. Therefore, if the relationship between the torque and the number of revolutions of an engine when the propeller efficiency is maximum in a full-power mode is examined to recognize a certain low therein, the law may be applied to the engine condition in a partial-power mode to enable maximization of the propeller efficiency in the partial power mode.
On the assumption that the propeller efficiency could be improved in this manner, the inventors of the present invention have studied the relationship between the number of revolutions and the torque of an engine when the propeller efficiency is maximum in a full-power mode, as described below in detail.
(1) Full-Power Mode
In the graph of FIG. 1, the power coefficient Cp, the advance ratio J, the propeller efficiency (%) and the propeller pitch angle xcex2 are non-dimensionally expressed with respect to an airplane having a normal aspiration engine. An optimal-efficiency condition of a propeller in a full-power mode has been confirmed in the relationship between the power coefficient Cp and the advance ratio J shown in the graph.
The axis of ordinate represents the power coefficient Cp and the axis of abscissa represents the advance ratio J. The propeller pitch angle xcex2 and the propeller efficiency % are also shown in the graph.
In the graph, a coordinate point {circle around (1)} is marked to indicate a condition at a time when the airplane takes off with full power. When the engine operates in the full-power mode, the rated output of the engine is fully extracted. The torque and the number of revolutions are previously set in the engine. Just at the time of leaving the ground, the given power coefficient Cp is uniquely determined since the atmospheric density xcfx81 is constant, and since the diameter D of the propeller is fixed. The determined value of the power coefficient Cp is marked with the coordinate point {circle around (1)}.
Thereafter, if the airplane continues taking-off by operating its engine in the full-power mode without changing the number of revolutions, its speed becomes higher and the advance ratio J also becomes higher according to the advance ratio equation shown above.
Thus, as is apparent from the graph, the advance ratio J represented by the axis of abscissa increases with the acceleration of the airplane while the power coefficient Cp represented by the axis of ordinate is constant. As indicated by the arrow A in the graph, the advance ratio J increases as the flight proceeds. Thereafter, a predetermined value of the advance ratio J is reached at a coordinate point {circle around (2)} simultaneously with proceeding from an accelerating condition into a constant-speed condition at a predetermined altitude.
In this process, if constant-speed control of the propeller with the governor is being performed, the combination of the torque and the number of revolutions is not changed, so that the power coefficient Cp is constant. In this process, the atmospheric density xcfx81 changes since the altitude of the airplane increases. However, in the case of the normal aspiration engine, the engine torque becomes lower in proportion to the atmospheric density xcfx81. Therefore, the power coefficient Cp is constant irrespective of the atmospheric density xcfx81. Also, the advance ratio J is constant.
During proceeding from the coordinate point {circle around (1)} to the coordinate point {circle around (2)}, the propeller pitch angle xcex2 of the variable-pitch propeller provided on the airplane increases gradually from about 20 degrees at the coordinate point {circle around (1)} to about 28 degrees at the coordinate point {circle around (2)}.
Since as mentioned above the airplane is designed so that the propeller efficiency is maximum when the engine operates with full power, the propeller efficiency is maximized in the full-power state corresponding to the coordinate point {circle around (2)}. In the state corresponding to the coordinate point {circle around (2)}, the airplane neither accelerates nor decelerates, so that the speed of the airplane is constant. The point {circle around (2)}, corresponding to the state in which the airplane neither accelerates not decelerates and in which the speed of the airplane is constant, is called a balance point because the thrust and the drag of airplane balance with each other.
This balance point is set by modeling of the airframe, the propeller and the engine. That is, the force (drag) produced as resistance of air according to the speed of the airplane to act on the airframe is basically proportional to the square of the speed of the airplane and is expressed by an equation: Dg=Kxcfx81V2. If the engine is a normal aspiration (NA) engine, it is presupposed that the engine torque is proportional to the atmospheric density. With respect to the propeller, a characteristic map of a three-blade propeller xe2x80x9cNACA5868-9xe2x80x9d has been used. If this propeller is used and if propeller efficiency maximum points are successively plotted in the relationship of the power coefficient and the advance ratio, Cp and J form a line L6 shown in FIG. 1, such that they are in a relationship: Cp xe2x88x9d J1.66. Thus, in the case of the propeller xe2x80x9cNACA5868-9xe2x80x9d, the propeller efficiency is maximum if Cp and J are on the line L6.
(2) Partial-Power Mode
The propeller efficiency has been examined by setting a suitable balance point with respect to the above-described airframe, propeller and engine when partial power is set. The results of this examination are shown in the graphs of FIGS. 2 and 3.
FIG. 2 shows a state where 75% of the maximum power is set. Since the engine power is the product of the torque and the number of revolutions as mentioned above, there are two cases of partial power setting: one in which the torque value is reduced; and one in which the number of revolutions is reduced. From this viewpoint, balance points respectively set in such two cases are marked in FIG. 2.
A point {circle around (3)} represents a 75%-power balance point when the engine is in a high-rotational-frequency low-torque condition, and a point {circle around (4)} represents a 75%-power balance point when the engine is in a low-rotational-frequency high-torque condition.
FIG. 3 shows a state where 50% of the maximum power is set. Similarly, a point {circle around (5)} represents a 50%-power balance point when the engine is in a high-rotational-frequency low-torque condition, and a point {circle around (6)} represents a 50%-power balance point when the engine is in a low-rotational-frequency high-torque condition.
These balance points {circle around (3)} to {circle around (6)} have been each identified as a point deviating from the propeller efficiency maximum line L6.
FIG. 4 shows the points {circle around (3)} to {circle around (6)} in a state of being plotted on the same graph. It has been confirmed that, as shown in FIG. 4, the propeller efficiency maximum point {circle around (2)} in the full-power mode is also located on the same line (Cp xe2x88x9d J3). Therefore, it is thought that, also in the partial-power mode, the propeller efficiency can be maximized with respect to any partial power if the condition corresponding to the point {circle around (2)} in the full-power mode can be maintained by suitably setting the torque and the number of revolutions.
(3) Relationship Between Torque and Number of Revolutions at Full-Power Point {circle around (2)}.
As described above, both of the power coefficient Cp and the advance ratio J are constant at the point {circle around (2)}. Therefore, it is thought that maximization of the propeller efficiency can be accomplished even in a partial-power mode as a result of special engine control such that both of the power coefficient Cp and the advance ratio J are constant.
The power coefficient Cp at the point {circle around (2)} will first be considered.
As described above, the power coefficient Cp is expressed by the following equation:       Cp    ⁢          xe2x80x83        ⁢          (              Power        ⁢                  xe2x80x83                ⁢        Coefficient            )        =            2      ⁢              xe2x80x83            ⁢      π      ⁢              xe2x80x83            ⁢      Te              ρ      ⁢              xe2x80x83            ⁢              N        2            ⁢              D        5            
The atmospheric density xcfx81 in this case is constant since the flight altitude is constant; D in this equation is uniquely determined if a predetermined propeller is specified; and 2xcfx80 is a constant. Accordingly, the torque Te and N2 of the number of revolutions N are in proportion. Consequently, a relational expression shown below is established between the engine torque and the number of revolutions at the point {circle around (2)}.
Te xe2x88x9d xcfx81N2 
The advance ratio J at the point {circle around (2)} will next be considered.
A state where the advance ratio J is constant indicates balance between the thrust and the force produced as resistance of air according to the speed of the airplane to act on the airplane, i.e., the drag, as described above. It can be said that the point {circle around (2)} is xe2x80x9ca point corresponding to a state where the drag and the thrust balance with each otherxe2x80x9d.
A precondition for improving the fuel efficiency and the operating efficiency of the airframe and the engine of an airplane as a whole including the propeller efficiency, i.e., increasing the flight distance traveled by the airplane consuming a predetermined amount of fuel, is not that the above condition be satisfied only for an instant in the engine condition during acceleration or deceleration, but that the drag of airplane and the thrust balance each other in the course of operation.
That is, to ensure that a certain engine operating condition can be set and continuously maintained to achieve the maximum operating efficiency of the entire airplane, balance between the drag of airplane and the thrust is required.
Therefore, if the relational expression: Te xe2x88x9d xcfx81N2 is satisfied, it is necessary to further examine whether the point {circle around (2)} can be included as a balance point. For example, in a case where partial power which is xc2xd of the maximum power is set, it is necessary that the relationship: Te xe2x88x9d xcfx81N2 be established, and that the point {circle around (2)} be included as a balance point.
It is assumed here that partial power is set by setting the number of revolutions to xc2xd of the maximum number of revolutions.
As described above, it is first conditioned that the advance ratio J be constant. Accordingly, if the number of revolutions is reduced to xc2xd, the airplane speed V becomes xc2xd according to the following equation:       J    ⁢          xe2x80x83        ⁢          (              Advance        ⁢                  xe2x80x83                ⁢        Ratio            )        =      V    ND  
Then, the drag of airplane becomes xc2xc according to the following equation:
Dg=Kxcfx81V2
The thrust will next be considered.
Te=N2 is assumed by removing the atmospheric density xcfx81 from Te=xcfx81N2 because the altitude is constant. Then the torque becomes xc2xc. It has been confirmed that the propeller thrust also becomes xc2xc according to the following equation:
Th=Texc2x7Ct/(Cgxc2x7D)
where Th is the thrust, Ct is a thrust coefficient, Cg is a torque coefficient, and D is the propeller diameter.
FIG. 7 shows equations for detailed representation of the airplane speed (1), the drag of airplane (2), the engine torque (2), and the propeller thrust (4), from which the above-described balancing relationship between the drag of airplane and the thrust has been obtained.
In the equations shown in FIG. 7, Te1 and N1 respectively represent the torque and the number of engine revolutions corresponding to 100% power. Also, the number of engine revolutions N2 is assumed to be 1/K of N1. Accordingly, N2=1/Kxc2x7N1 is presupposed.
From the above-described study, it has been confirmed that, since the above-described propeller efficiency maximum point {circle around (2)} is a point at which both of the power coefficient Cp and the advance ratio J are constant, maximization of the propeller efficiency can be accomplished even in a partial-power mode as a result of special engine control such that both of the power coefficient Cp and the advance ratio J are constant.
It has also been confirmed that a setting can be determined such as to maximize the propeller coefficient if the engine is controlled so as to satisfy the condition that the power coefficient Cp be constant, that is, xe2x80x9cthe torque be proportional to the square of the number of revolutionsxe2x80x9d (Te xe2x88x9d N2). Further, it has been confirmed that such control results in a state where the drag of airplane and the thrust balance with each other.
A conclusion is that, with respect to a normal aspiration engine, it is possible to maximize the propeller efficiency by controlling the engine so as to satisfy the condition that xe2x80x9cthe torque be proportional to the square of the number of revolutionsxe2x80x9d (Te xe2x88x9d N2) at the time of partial power setting.
As a result, in the case of a normal aspiration engine, the torque Te and the number of revolutions N that maximize the propeller efficiency can be determined by the above relational expression after determination of desired partial power, as shown in FIG. 8. Referring to Table 1, in the above-described case of setting 75% power, the torque is 82% and the number of revolutions is 91%. In the case of 50% power, the torque is 63% and the number of revolutions is 79%.
An engine having a turbocharger has no such change in torque as that in a normal aspiration engine due to a change in the atmospheric density, because it is boosted when the atmospheric density is reduced at a certain altitude.
Therefore, there is a need for correction by the atmospheric density xcfx81 in the above-described relational expression of the torque and the number of revolutions in setting the propeller efficiency maximum point in a partial-power mode, and the same relational expression as the relational expression: Te xe2x88x9d xcfx81N2 of the torque and the number of revolutions obtained from the above-described formula of the power coefficient Cp applies to an engine with a turbocharger.
The relationship between the torque and the number of revolutions, considered with respect to the maximum of the propeller efficiency of an airplane on which an engine with a turbocharger is mounted, changes with respect to the atmospheric density proportional to the altitude, as shown in the graph of FIG. 5. In the graph of FIG. 5, a line L4 indicates Te xe2x88x9d xcfx81N2 on the ground, and a line L5 indicates Te xe2x88x9d xcfx81N2 at an altitude of 15000 ft.
Consequently, in the above-described example, when 75% power is to be obtained at the altitude of 15000 ft at which the atmospheric density xcfx81 is 0.77 g/cm3, the torque is 82% and the number of revolutions is 91%, as shown in Table 2. When 75% power is to be obtained on the ground where the atmospheric density xcfx81 is 1.225 g/cm3, the torque is 88% and the number of revolutions is 85%, as shown in Table 2.
When such partial power is set, the torque is reduced, as mentioned above. Therefore, there is a possibility of the engine efficiency, i.e., the fuel efficiency of the engine, being reduced. This problem can be solved by combining lean burn control with the above-described engine control.
(3) When Airplane Drag Changes
Correction of the propeller efficiency maximum point in a case where the drag of airplane changes during a flight will next be considered.
For example, if the weight of an airplane is changed during a flight, the speed of the airplane is also changed. Correspondingly, the drag of airplane is changed according to the above equation Dg=Kxcfx81V2. In this case, a balance point at which the thrust and the drag of airplane balance with each other is also changed to deviate from the above-described propeller efficiency maximum point.
A case where the weight of an airplane advancing with the maximum propeller efficiency at a point {circle around (1)}, as shown in the graph of FIG. 6, is reduced will be considered by way of example.
If the weight of the airplane is reduced in such a situation, the speed of the airplane is increased, so that the advance ratio J represented by the axis of abscissa of the graph increases. Accordingly, the balance point {circle around (1)} moves toward the high-airplane-speed low-rotational-frequency side of the graph to change to a new balance point {circle around (3)} while the power coefficient represented by the axis of ordinate is constant. It is apparent that the new balance point {circle around (3)} after the load change is off the above-described propeller efficiency maximum line (Cp xe2x88x9d J1.66).
In this case, when the propeller efficiency maximum point in the above-described partial-power mode is checked, the combination of the torque and the number of revolutions is changed so as to maintain the predetermined constant power, thereby plotting a series of points forming a line indicating Cp xe2x88x9d J3.
That is, the combination of the torque and the number of revolutions is changed under the constant-power condition to extend the Cp xe2x88x9d J3 line from the balance point {circle around (3)} after the load change to determine a point at which the Cp xe2x88x9d J3 line intersects the propeller efficiency maximum line (Cp xe2x88x9d J1.66). This point of intersection can be set as a balance point {circle around (5)} corresponding to the maximum of the propeller efficiency after the load change.
In practice, data on the propeller efficiency maximum line (Cp xe2x88x9d J1.66) is stored in advance in a random access memory (RAM) provided in an electronic control unit (ECU) mounted on the airplane. With respect to the balance point {circle around (3)} after the load change, the advance ratio J is computed from the airplane speed measured by a speed sensor and the number of engine revolutions, and the power coefficient is obtained from a map stored in the RAM of the ECU by referring to the number of engine revolutions.
Also in a case where the weight of the airplane is increased, the combination of the torque and the number of revolutions is changed under the constant-power condition from a balance point {circle around (2)} after the load increase to determine a point of intersection with the propeller efficiency maximum line (Cp xe2x88x9d J1.66), thereby setting a balance point {circle around (4)} corresponding to the maximum of the propeller efficiency after the load change.
The combination of the torque and the number of revolutions at the intersection point can be determined.
As described above, the propeller efficiency maximum point after a load change is determined in this way, the engine torque and the number of revolutions at the propeller efficiency maximum point are determined and partial power correction of the torque and the number of revolutions is performed, thus enabling engine control with an optimal operating efficiency after the change in the load on the airplane.
The above is the principle of the present invention. The present invention can therefore be applied to either a normal aspiration engine or an engine having a turbocharger. Specific techniques for the above-described engine control will be described below with respect to preferred embodiments of the invention.
According to the present invention, there is also provided an apparatus for controlling a reciprocating engine with a variable-pitch propeller provided on an airplane, the apparatus comprising a throttle unit for setting the amount of air supplied to the engine, a fuel regulator for controlling the air-fuel ratio for the engine, a governor for controlling the number of revolutions of the propeller, one power control lever capable of setting desired engine power, and control means provided in association with the operating lever, the throttle unit, the fuel regulator and the governor, the control means having an air-fuel ratio map, a throttle opening map and an engine revolution map formed so as to enable setting of an engine torque Te and a number of engine revolutions N such that a relationship expressed by Te xe2x88x9d N2 is established, the control means being capable of outputting, to the throttle unit, the fuel regulator and the governor, control values by comparing information about partial power selected by the operating lever with each of the maps, the control values being such that the propeller efficiency is maximized when predetermined partial power is set.
The above-described airplane engine control apparatus also has a sensor for measuring the opening angle of the operating lever. The above-described control means includes means for outputting, to the throttle unit, the fuel regulator and the governor, control values by comparing each of the maps and partial power information including the opening angle value of the operating lever measured with the sensor, the control values being such that the propeller efficiency is maximized when predetermined partial power is set.
The above-described airplane engine control apparatus also has a sensor for measuring the number of engine revolutions. The above-described control means includes means for outputting, to the throttle unit, the fuel regulator and the governor, control-values by comparing each of the maps and partial power information including the number of engine revolutions measured with the sensor, the control values being such that the propeller efficiency is maximized when predetermined partial power is set.
According to the present invention, there is further provided an apparatus for controlling a reciprocating engine with a variable-pitch propeller and a turbocharger provided on an airplane, the apparatus comprising a throttle unit for setting the amount of air supplied to the engine, a fuel regulator for controlling the air-fuel ratio for the engine, a governor for controlling the number of revolutions of the propeller, a boost pressure setting device capable of controlling the boost pressure of the turbocharger, one power control lever capable of setting desired engine power, measuring means capable of measuring the opening angle of the power control lever, and control means provided in association with the operating lever, the throttle unit, the fuel regulator and the governor, the control means having an air-fuel ratio map, a throttle opening map, an engine revolution map and a boost pressure map set so as to enable setting of an engine torque Te and a number of engine revolutions N such that a relationship expressed by Te xe2x88x9d xcfx81N2 is established, the control means being capable of outputting, to the throttle unit, the fuel regulator and the governor, control values by comparing each of the maps and the opening angle value of the operating lever measured by the operating lever measuring means, the control values being such that the propeller efficiency is maximized when predetermined partial power selected by the operating lever is set.
An atmospheric density compensation mechanism is provided between the power control lever and the throttle unit, and the atmospheric density compensation mechanism may be constituted of a bellows mechanism capable of adjusting the opening angle value of the operating lever in accordance with the atmospheric density.
The atmospheric density compensation mechanism may have an air pressure sensor capable of measuring atmospheric pressure, a throttle actuator capable of adjusting the throttle opening, and control means capable of controlling the amount of drive of the throttle actuator on the basis of the value of atmospheric pressure measured with the air pressure sensor, and may control the opening angle of the operating lever in accordance with the atmospheric density.
The configuration and specific components of airplane engine control apparatuses in accordance with the present invention will be described below with respect to embodiments of the invention.